High energy-based scanners are known in the art. Such scanners employ, for example, X-rays to scan an object of interest. This typically involves using a plurality of detector elements to detect the intensity of the scanning energy as the latter interacts with the object of interest.
In many cases, the detector elements for a given high energy-based scanner are not perfectly evenly spaced. The spacing irregularities may be either gradual or abrupt (the tendency of any given detector will generally depend on its construction details). These spacing irregularities, in turn, can result in distorted scanning results. When applied in a computed tomography (CT) application setting, for example, spacing irregularities can result in warped reconstructed images and/or an inclusion of artifacts in the image such as blurring, streaking, rings, or doubling. When applied in a digital radiography (DR) application setting, such irregularities can prevent accurate image registration, can prevent one from truly resampling to a uniform flat imaging plane, and/or may be visually distracting and/or annoying.
As a result, it is also known to calibrate the processing steps as are employed to process scanning output to attempt to accommodate the inherent distortion as is associated with a given high energy-based scanner. By one approach, this has comprised conducting a fixed position scan of a fixed array or grid of equally spaced vertical wires (presuming, of course, that the channels are horizontally arranged) and measuring the channel number locations of each wire. Interpolation is then used to form a distortion correction table. By another approach (used in particular for translate-rotate computed tomography), one conducts a translation of an off-center pin, repeating for 8 equally spaced rotation positions, measuring the trajectory of the pin through each of the 8 scans, measuring several statistics from this trajectory, and returning an estimated distortion measurement as a result.
Though effective to a point, such approaches nevertheless are not fully satisfactory. The approaches that rely upon a vertical wire grid suffer in that non-zero width wires yield poor accuracy in that it can be difficult to accurately find the center of the wire with sub-pixel resolution. Spacing between the wires also contributes to poor resolution as one cannot capture discrete distortions or quickly (that is, abruptly) changing continuous distortions. Also, approaches that rely upon wire grids are not practical for use in large scanning systems (such as some of those employed for industrial or security purposes. Furthermore, approaches that require rotation are of course not suitable for systems that do not support rotation (such as DR-only systems) while approaches that require translation are not suitable for systems that do not support translation (such as most DR-only systems and rotate-only CT scanners).
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions and/or relative positioning of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention. It will further be appreciated that certain actions and/or steps may be described or depicted in a particular order of occurrence while those skilled in the art will understand that such specificity with respect to sequence is not actually required. It will also be understood that the terms and expressions used herein have the ordinary technical meaning as is accorded to such terms and expressions by persons skilled in the technical field as set forth above except where different specific meanings have otherwise been set forth herein.